Many electro-magnetic type fuel injectors include a spring that urges a pintle/ball assembly against a nozzle seat to prevent fuel from flowing from the injector when the injector is OFF. When a current is applied to a coil winding within the fuel injector, a magnetic field is generated that urges the pintle/ball assembly away from the nozzle seat and thereby turns the injector ON. In general, the amount of force needed to lift a pintle/ball assembly from the injector OFF or closed position to the injector ON or open position is proportional to a spring load and rate of the spring plus a fuel pressure of the fuel present in the injector. However, some direct injection fuel systems have increased fuel pressures to a level where it becomes difficult to provide a fuel injector that has the same physical outline or package size as injectors designed for lower fuel pressure levels, and is able to reliably ‘dead lift’ the pintle/ball assembly at the higher fuel pressure levels.
It has been proposed to add a sliding or flying armature that, in response to the magnetic field, accelerates and then strikes a pintle stop like a slide hammer to provide a combination of kinetic energy and static force to lift the pintle/ball assembly off the nozzle seat. It has also been proposed to include an armature spring to urge the armature away from the pintle stop so that for each injection event the armature consistently has the greatest distance to accelerate before striking the pintle stop. However, the addition of this armature spring undesirably increases the cost and complexity of the fuel injector and reduces the performance of the injector with regard to pintle opening rate and pintle opening delay.